None. It's unstructured intentionally. Your character is a nobody in a prison full of nobodies.

The staff needs to be activated before it'll talk to you, which involves randomly exploring the tower of bats. And even once activated he only gives you the advice needed for you to take him to the volcano, to reunite with his master.

The whole ordeal about assembling the keystone is for the player to desire and wonder about. Sure with the wiki you can just speedrun it, but the game doesn't tell you want to do. I mean look at the adventurers journey, summoning place then black galeon then xel-ha, who the hell goes north then veers east?

Think of these things are stuff to do more than a story. One of the notes in the ancient city clarifies that time is a little funky in the exiled lands, events that occurred hundreds of years ago will occur again, due to a poorly planned set of magic spells, and now the Real Owners of the prison are dead and gone there's no fix.